Welding QC Interview Questions Answers

This article is about Welding QC Interview Questions Answers for international projects and ARAMCO SABIC CBT Test.

1) What is the formula for heat input?

The correct formula for heat input is:

Heat Input (Joules per centimeter) = (Voltage x Amperage x 60) / Travel Speed (centimeters per minute)

Please note that the formula calculates the heat input in Joules per centimeter. The variables used in the formula are:

Voltage: The welding voltage in volts.
Amperage: The welding current in amperes.
Travel Speed: The welding travel speed in centimeters per minute.

2) How do you calculate the weld repair percentage?

The formula for calculating the weld repair percentage is as follows:

% RR = (Lr / Lw) x 100

Where: % RR represents the percent repair rate. Lr is the total length of repair in one week. Lw is the total length of weld radiographed in one week.

To calculate the weld repair percentage, divide the total length of repair by the total length of weld radiographed and then multiply by 100 to express it as a percentage.

3) What should be the distance b/w two parallel welds?

The distance between two parallel welds should be either 20mm or three times the wall thickness of the joint, whichever value is greater. This requirement helps ensure proper spacing between welds to maintain structural integrity and prevent interference or overlap between adjacent welds.

4) What are the types of thermocouples in PWHT?

The types of thermocouples commonly used in post-weld heat treatment (PWHT) are:

Type K (Chromel-Alumel): This is the most commonly used thermocouple in industrial applications. It consists of chromel (nickel-chromium alloy) and alumel (nickel-aluminum alloy) wires. It has a wide temperature range and good accuracy.
Type J (Iron-Constantan): This thermocouple is composed of iron and constantan (copper-nickel alloy) wires. It has a more limited temperature range compared to Type K, but it offers good sensitivity and stability.

5) What is HIC?

HIC stands for Hydrogen Induced Crack. It refers to a form of cracking that occurs in metals, particularly carbon and low-alloy steels, when they are exposed to hydrogen. HIC is a result of the ingress and diffusion of hydrogen into the metal, which can happen during various stages of fabrication, operation, or maintenance.

6) Different categories of fluid services in ASME B 31.3?

In ASME B31.3, the code that specifically addresses the design, construction, and maintenance of process piping systems, there are different categories of fluid services that help classify the severity and conditions of the fluid being transported. These categories are as follows:

Category D: This category refers to the most severe fluid service conditions. It includes fluids that are highly toxic, highly corrosive, or flammable. These fluids pose a significant risk to personnel, equipment, and the environment.
Category M: This category includes fluids that are moderately severe. They may be moderately toxic, moderately corrosive, or flammable, but to a lesser extent than those in Category D. The precautions and design considerations for Category M fluids are less stringent compared to Category D.
High-Pressure Fluid Service: This category encompasses fluids that operate at high pressures. The design and construction requirements for piping systems carrying high-pressure fluids are more stringent due to the increased potential for failure and the associated risks.
Normal Fluid Service: This category includes fluids that do not fall under Category D or Category M. These are typically fluids that are non-toxic, non-corrosive, and non-flammable, posing minimal risk to personnel and equipment.

7) What is ocv and ccv?

OCV (Open Circuit Voltage) refers to the voltage between the welding power source and the welding electrode when no arc is established. It is the voltage present in the welding circuit when the welding machine is turned on but no welding is taking place. OCV is used to set the initial voltage level before striking an arc.

CCV (Closed Circuit Voltage), on the other hand, refers to the voltage across the welding circuit when an arc is established between the welding electrode and the workpiece. It is the voltage that is maintained during the welding process. CCV plays a crucial role in determining the heat input and penetration depth during welding.

8) What are the types of olets?

The term “olet” refers to a type of branch connection used in piping systems. There are several types of olets commonly used, including:

Weldolet: A Weldolet is a welding outlet that is welded onto the main pipe. It has a beveled end that is designed to be butt-welded to the pipe, providing a branch connection.
Sockolet: A Sockolet is a socket weld outlet that is used to create a branch connection by socket-welding the olet onto the main pipe. It has a socket-shaped end that fits over the pipe, allowing for easy installation.
Threadolet: A Threadolet is a threaded outlet that can be screwed onto the main pipe. It has a threaded end that allows for a threaded connection to be made, providing a branch connection.
Nippolet: A Nippolet is similar to a Weldolet but with a socket end. It is designed for socket-welding onto the main pipe, creating a branch connection.

9) What factors are taken into account when selecting and designing a joint for a welding application?

When selecting and designing a joint for a welding application, several factors are taken into account. Here are four important factors:

Strength: The joint should be designed to provide sufficient strength to withstand the applied loads and meet the required structural integrity. Factors such as the material properties, joint configuration, and welding process influence the joint’s strength.
Accessibility for Welding: The joint should be designed in a way that allows for easy access during the welding process. Sufficient space and clearance must be provided to ensure proper weld bead placement and adequate penetration. Complex joint geometries may require specialized welding techniques or equipment.
Minimize Distortion: Welding can introduce thermal stresses and distortion into the joint and surrounding areas. Minimizing distortion is important to maintain dimensional accuracy and prevent undesirable effects on the overall structure. Proper joint design, welding sequence, and use of pre- and post-welding techniques like preheating and post-weld heat treatment can help reduce distortion.
Cost of Welding: The cost of welding includes factors such as labor, equipment, consumables, and inspection. Joint design can impact the welding time, complexity, and the amount of filler material required. Designing a joint that minimizes welding costs while meeting the required specifications and quality is a key consideration.
Accessibility for Inspection: The joint should allow for effective inspection to ensure the quality and integrity of the weld. Sufficient access should be provided for non-destructive testing (NDT) methods like visual inspection, radiography, ultrasonic testing, or magnetic particle testing to detect any potential defects or discontinuities.

10) What is the P no for SS & CS?

The P-number, or “P-Number,” is a designation used in ASME BPVC Section IX to identify the grouping of materials for welding procedure qualification. Here are the P-numbers for Stainless Steel (SS) and Carbon Steel (CS):

Stainless Steel (SS): P-Number 1
Carbon Steel (CS): P-Number 8

The P-number classification system helps in determining the essential variables for welding procedures, such as base metal thickness, welding process, and preheat requirements. Each P-number represents a specific group of materials that have similar welding characteristics and properties.

11) What are supplementary essential variables?

Supplementary essential variables refer to specific welding conditions or parameters that, when changed, can affect the notch toughness properties of a weldment. These variables are considered additional essential variables that need to be controlled and qualified during welding procedures. They are typically identified and specified in welding codes and standards to ensure the integrity and quality of the welded joints.

12) What are essential variables?

Essential variables refer to specific welding conditions or parameters that, when changed, can significantly impact the mechanical properties of the weldment or the ability of a welder to produce sound welds. These variables are considered crucial and must be carefully controlled and qualified during welding procedures. Essential variables are typically identified and specified in welding codes and standards to ensure the quality and integrity of welded joints.

There are two types of essential variables: procedure essential variables and performance essential variables.

Procedure Essential Variables: These variables are related to the welding procedure and affect the mechanical properties of the weldment. Examples of procedure essential variables include:
- Base metal thickness
- Welding process (e.g., SMAW, GTAW, etc.)
- Preheat and interpass temperature
- Welding position (e.g., flat, horizontal, vertical, overhead)
- Filler metal type and classification
- Heat input
Performance Essential Variables: These variables are related to the welder’s ability to produce sound welds. They affect the quality and integrity of the weld. Examples of performance essential variables include:
- Welder qualification (e.g., certification, skill level)
- Welding position (e.g., flat, horizontal, vertical, overhead)
- Welding technique and manipulation
- Visual inspection criteria and acceptance standards

13) Which standard do you refer for the welding equipment calibration?

While BS 7570 is a standard related to calibration, it specifically pertains to the calibration of electrical measuring instruments. It does not specifically address welding equipment calibration. When it comes to welding equipment calibration, there are several relevant standards that can be referred to, depending on the specific equipment being calibrated. Some commonly referenced standards for welding equipment calibration include:

ISO 17662: Welding — Calibration, verification and validation of equipment used for welding, including ancillary activities.
ISO 15614-12: Specification and qualification of welding procedures for metallic materials — Welding procedure test — Part 12: Calibration of equipment used for welding.
AWS C3.7: Recommended Practices for Calibration and Certification of Welding Equipment.

14) What are the tests required for verifying supplementary essential variables?

While notch toughness tests such as Charpy V-notch test and drop weight test are commonly used to evaluate the impact toughness properties of materials, they are not specifically used for verifying supplementary essential variables in welding. Supplementary essential variables are related to the changes in welding conditions that affect the notch toughness properties of a weldment, rather than the base material.

To verify supplementary essential variables in welding, the following tests and examinations may be conducted:

Tensile Test: This test measures the strength and ductility of the welded joint and can help evaluate the effect of welding conditions on the mechanical properties.
Bend Test: It assesses the ductility and soundness of a welded joint by subjecting it to bending forces.
Macroscopic Examination: This examination involves visual inspection of the welded joint to identify any macroscopic defects such as cracks, lack of fusion, or incomplete penetration.
Hardness Test: This test measures the hardness of the welded joint and can indicate the degree of heat-affected zone (HAZ) softening or potential for hydrogen-induced cracking.
Radiographic Examination: It uses X-rays or gamma rays to inspect the internal structure of a welded joint and identify any discontinuities or defects.
Ultrasonic Testing: It utilizes sound waves to detect internal defects, such as cracks or porosity, in the welded joint.

15) What is a welding procedure specification (WPS)?

A Welding Procedure Specification (WPS) is a document that provides detailed instructions and guidelines for performing a specific welding operation. It is developed based on applicable codes, standards, and engineering requirements. The WPS serves as a reference for welders to ensure consistent and quality welds are produced.

The key components of a WPS include:

Welding Process: Specifies the welding process to be used, such as Shielded Metal Arc Welding (SMAW), Gas Tungsten Arc Welding (GTAW), or others.
Materials: Specifies the base metal and filler metal to be used, including their specifications and grades.
Joint Design: Describes the configuration and preparation of the joint, such as bevel angles, groove dimensions, or joint type.
Welding Parameters: Provides specific details on welding variables, such as voltage, current, travel speed, preheat temperature, interpass temperature, and post-weld heat treatment requirements.
Welding Technique: Describes the welding technique to be employed, such as weaving pattern, number of passes, and any special considerations.
Acceptance Criteria: Specifies the quality and inspection requirements, including any non-destructive testing (NDT) methods and acceptance criteria for the completed welds.
Essential Variables: Identifies the essential variables that must be maintained during welding to ensure the desired mechanical properties of the weldment.
Qualification: Indicates the test and performance requirements that the welder and the welding procedure must meet to be qualified.

Welding QC Interview Questions Answers – Aramco CBT